Work machines such as, for example, dozers, loaders, excavators, motor graders, and other types of heavy machinery use hydraulic actuators coupled to a work implement for manipulation of a load. Such work machines generally do not include shock absorbing systems and thus may pitch, lope, or bounce upon encountering uneven or rough terrain. The substantial inertia of the work implement and associated load may tend to exacerbate these movements resulting in increased wear of the work machine and discomfort for the operator.
One method of reducing the magnitude of the movements attributable to the work implement and associated load is described in U.S. Pat. No. 5,733,095 (the '095 patent) issued to Palmer et al. on Mar. 31, 1998. The '095 patent describes a work machine with a ride control system having a three-way solenoid-actuated directional control valve connected to move a hydraulic actuator in response to movements of a control lever, and a ride control arrangement. The ride control arrangement includes a valve mechanism associated with the hydraulic actuator and an accumulator. The valve mechanism includes a first valve and a second valve. The first valve is movable to selectively control fluid flow from the hydraulic actuator to the accumulator or to a reservoir. The second valve is controlled to move the first valve, thereby providing ride control. When the first valve is moved to communicate fluid from the hydraulic actuator to the accumulator, movement of a work implement connected to the hydraulic actuator is cushioned by flow between the hydraulic actuator and the accumulator. Consequently, the force of a load associated with the work implement is prevented from transference to a frame of the work machine to cause a jolt thereto and subsequently to wheels of the work machine, which could cause the work machine to lope or bounce.
Although the ride control system of the '095 patent may reduce some undesired movements of the work machine, it may be complex, expensive, and lack precision and responsiveness. In particular, because the '095 patent uses different types of valves to actuate the hydraulic actuator and to provide ride control, the system may be complex to control and expensive to build and maintain. Further, because the directional control valve is a three-position valve that controls both a filling function and a draining function associated with the hydraulic actuator, it may be costly and difficult to precisely tune.
The disclosed hydraulic system is directed to overcoming one or more of the problems set forth above.